Corner protector attachment method and apparatus for frames having non-rectangular cross-section moldings

ABSTRACT

A method and apparatus for bending a flat cardboard preform into a corner protector that encloses and protects a corner of a picture frame from impact damage during shipping and handling of the frame includes positioning symmetrically between the corner and preform a thin, wedge-shaped template plate having a forwardly protruding, right-triangularly shaped vertex angle. Bending motion of corner protector cover flap sections upward from the plane of the preform is limited by contact of the flap sections with edges of the template plate to perpendicular positions relative to the plane of the preform, thus assuring that channel-shaped protective covers for sides of the frames formed by subsequent inwardly and downwardly bending of upper end portions of the flap sections to overlie a face surface of the frame will have rectangular cross sections, even if the sides of the frame are non-rectangular, e.g., angled or contoured.

BACKGROUND OF THE INVENTION

[0001] A. Field of the Invention

[0002] The present invention relates to methods, apparatus and articles for protecting the corners of rectangularly-shaped picture frames from impact damage during shipment and handling. More particularly, the invention relates to a method and apparatus for attaching protective covers to the corners of ornate frames having non-rectangular cross section moldings, of the type used to hold pictures, bulletin boards, mirrors, windows and the like.

[0003] B. Description of Background Art

[0004] Picture frames for holding and displaying paintings, photographs, diplomas, certificates and similar flat articles are manufactured in prodigious quantities worldwide. Although picture frames vary in shape and construction details, most frames have a rectangular plan view shape. Moreover, the structure of most picture frames consists essentially of four straight channel members or moldings, each having an inner channel that intersects channels of adjacent members at a ninety degree angle. Four such channel members fastened together form a rectangular ring-shaped frame. The four channels or recesses in the moldings together comprise a rectangular ring-shaped space for receiving a rectangularly-shaped flat display piece such as a photograph or painting, and sometimes, a backing panel, mat and protective cover glass.

[0005] Picture frames of the type described above are made from a variety of materials including, wood, metal and plastic. Whatever material the frame is made of, the geometry of a rectangular picture frame dictates that it have four peripheral members of generally uniform thickness and joined to each other at four-five degree mitre angles to form ninety degree corners. These corners protrude, and are therefore highly subject to breakage, denting or cosmetic damage during shipment. Accordingly, most picture frames, whether empty or occupied, are fitted with some sort of corner protectors during shipment. Such corner protectors are usually made of a relatively inexpensive recyclable material such as cardboard or polystyrene foam.

[0006] In U.S. Pat. No. 6,018,934, issued Feb. 1, 2000, the present inventor disclosed a method and apparatus for installing covers onto the corners of frames for pictures and the like, to protect the corners from damage during shipment and handling. The disclosed method and apparatus uses thin, flat cardboard preforms which have symmetric right triangularly-shaped left and right portions which become lower and upper protective cover flaps for a corner of a frame when folded around the corner in the manner described below. The two triangular cover flaps are joined at vertical sides thereof to opposite vertical sides of a vertically elongated, rectangularly-shaped, first, “spine” edge cover flap. The left or lower triangular cover flap of the preform has depending outwardly from its horizontal base edge a horizontally elongated rectangularly-shaped, second, “pendent” edge cover flap, and depending outwardly from an outer horizontal edge of the second edge cover flap, a trapezoidally-shaped securement flap.

[0007] According to the method disclosed in U.S. Pat. No. 6,018,934, a flat cardboard preform of the type described above is positioned above the corner of a rectangular frame, such as a picture frame with perpendicularly intersecting side edges of the frame vertically aligned with the perpendicular intersecting sides of the left, lower right triangularly-shaped cover flap. The apparatus disclosed in the '934 patent includes two flap folder mechanisms, each including a rectangular flap folder arm which fits into a separate rectangularly-shaped recess in the upper surface of a worktable which comprises part of the apparatus. Each flap folder mechanism includes linear and rotary actuators which elevate and rotate the flap folder arm.

[0008] A first flap folder mechanism elevates a first flap folder arm, thereby elevating a pendent edge cover flap and securement flap of the preform into a vertical position adjacent to a first side edge of a frame corner, and rotates the arm ninety degrees inwardly towards the frame, to thereby bend the pendent edge corner flap and securement flap to form with the lower cover flap a first C-shaped or U-shaped channel which encloses a triangularly-shaped corner portion of the lower face, a vertical side of a first molding, and upper side of the first molding of the frame. A second flap folder mechanism then elevates a second flap folder arm, thereby elevating a spine edge cover flap and upper triangular cover flap of the preform, and rotates the arm ninety degrees inwardly towards the frame, to thereby bend the upper triangular cover flap and spine edge cover flap to form with the lower triangular cover flap a second C-shaped or U-shaped channel which encloses a triangularly-shaped corner portion of the upper facing side of the frame, and a side edge and upper face of a second frame molding. The apparatus includes a staple gun which inserts a staple downwardly through the upper triangularly-shaped cover flap and securement flap into the first frame molding, thereby securing the corner protector in a folded, protective position over the corner of the frame.

[0009] The method and apparatus for installing corner protectors onto picture frames disclosed in U.S. Pat. No. 6,018,934, have proved to be highly effective for use with frames having rectangular cross-section moldings. However, a problem existed for applications in which it was required to install a corner protector onto the corners of certain types of ornate frames which have sides which intersect at ninety degrees, but which have non-rectangularly-shaped transverse cross sectional shapes, such as fluted or curved shapes. It can be readily understood that conforming a C-shaped or U-shaped channel portion of a folded preform to an irregular, non-rectangular frame cross section is not feasible. Moreover, the elevation and rotation of a flap folder arm to bend a cardboard preform into a channel having sides that intersect at right angles on a frame having rectangular cross sectional shape frame molding members can result in unpredictable shapes when used on frames in which the moldings have non-rectangular cross sections. When preforms are bent into such irregular shapes, the finished protector has an unsightly appearance. More importantly, for some molding shapes, the protector may not completely cover a frame corner, and may also result in mis-aligning the corner protector flaps relative to the frame sufficiently to prevent proper attachment of the corner protector to the frame. The present invention was conceived of to provide an improved corner protector attaching method and apparatus which may be used effectively with ornate frames which have moldings that do not have rectangular cross-sections, as well as with more conventional frames in which the frame moldings have rectangular or square cross-sections.

OBJECTS OF THE INVENTION

[0010] An object of the present invention is to provide a method for attaching protective covers onto the corners of a rectangular frame, such as that used to hold a picture, which has side members or moldings which form a rectangular ring shape, but which may have non-rectangular cross-sections.

[0011] Another object of the invention is to provide an apparatus for automatically attaching protective covers onto the corners of frames which have non-square or square cross-sections.

[0012] Another object of the invention is to provide an apparatus for folding a flat sheet of flexible material over the corner of a picture frame formed by the intersection at right angles of a pair of frame side members or moldings which have an arbitrary, including non-rectangular, cross-sectional shape, and securing folded portions of the flexible material together to form a protective cover for the corner of the frame.

[0013] Another object of the invention is to provide an apparatus for bending a flat cardboard preform cut to a predetermined shape over the corner of a picture frame formed by the intersection of a pair of frame moldings having an arbitrary cross-sectional shape, and securing the folded portions of the cardboard preform to each other and to the frame to form a corner protector for the frame.

[0014] Another object of the invention is to provide a picture frame corner protector attaching apparatus which includes means for clamping and holding the corner of a frame, folding a preform made of a thin sheet of flexible material having a shape approximating that of a truncated isosceles triangle modified by the addition of a trapezoidally-shaped tab depending downwardly from one side of the base of the triangle into separate flaps which overlap adjacent edges and upper and lower faces of the corner of the frame, and fastening the flaps together and to the frame to form corner protectors for the frame corners.

[0015] Another object of the invention is to provide a method for folding a preform made of a thin sheet of flexible material into a protective cover which encloses a corner of a picture frame formed by the perpendicular intersection of a pair of frame moldings which have an arbitrarily contoured front surface, the method comprising the steps of placing a preform on a worktable with the perpendicular sides of a right triangular lower cover flap portion of the preform in a predetermined position, translating a frame front face down horizontally over said lower cover flap to bring sides and vertex of a frame corner into vertical overlying alignment with sides and vertex of the lower cover flap portion of the preform, translating a thin, uniform thickness wedge plate having in plan view the shape of an isosceles right triangle horizontally between the frame and preform to bring sides and vertex of said wedge plate into vertical alignment with respective sides and vertices of said preform and said frame corner, folding upwards from the plane of the preform a first, pendent edge cover flap and attached securement flap part to a vertical position pressed against a first side edge of the wedge plate, folding the securement flap perpendicularly inwards from the first, pendent edge cover flap to overlie a surface of an upwardly facing, rear surface of a first molding member of the frame, folding upwards from the plane of the preform a second, spine edge cover flap part and attached triangular upper cover flap part of the preform to a vertical position pressed against a second side edge of the wedge plate, folding the upper cover flap perpendicularly inwards from the vertical spine edge flap to overlie the securement flap, and fastening the securement flap to the first frame molding and to the upper cover flap.

[0016] Another object of the invention is to provide an apparatus for folding a preform made of a thin sheet of flexible material into a protective cover which encloses a corner of a picture frame formed by the perpendicular intersection of a pair of frame moldings which have an arbitrarily contoured front surface, the apparatus including a thin, uniform thickness wedge plate which has an end portion that has in plan view the shape of a right triangle, and a linear actuator for translating the wedge plate between and in vertical alignment with the inverted front face of the frame and a preform, the sides of the wedge plate providing abutting surfaces to limit inward movement of parts of the preform bent upwardly towards the frame, thereby ensuring that the bent sides remain vertical, and perpendicular to the plane of the preform.

[0017] Various other objects and advantages of the present invention, and its most novel features, will become apparent to those skilled in the art by perusing the accompanying specification, drawings and claims.

[0018] It is to be understood that although the invention disclosed herein is fully capable of achieving the objects and providing the advantages described, the characteristics of the invention described herein are merely illustrative of the preferred embodiments. Accordingly, I do not intend that the scope of my exclusive rights and privileges in the invention be limited to details of the embodiments described. I do intend that equivalents, adaptations and modifications of the invention reasonably inferable from the description contained herein be included within the scope of the invention as defined by the appended claims.

SUMMARY OF THE INVENTION

[0019] Briefly stated, the present invention comprehends a method and apparatus for installing protective cardboard covers over the corners of frames, of the type commonly used to hold pictures, bulletin boards, mirrors, windows and similar articles. The method and apparatus according to the present invention work effectively with rectangular plan view frames in which the frame members or moldings have various transverse cross-sectional shapes, including ornately curved or fluted front surfaces, as well as with conventional rectangular cross-sections.

[0020] The picture frame corner protector installation method and apparatus according to the present invention utilizes corner protectors which are folded or bent into shape from flat preforms consisting of thin sheets of cardboard, each pre-cut, by die cutting, for example, into a generally triangular shape which is modified to enable the preform to be bent over and enclose a corner, i.e., the vertex, and adjacent end portions of a pair of adjacent side channel members or moldings which intersect to form corner of a rectangularly-shaped picture frame. Four such corner protectors are used to cover the four corners of a frame.

[0021] In a preferred embodiment of the invention the plan view shape of the corner protector preform is that of two mirror symmetric, left and right, right-triangularly-shaped flaps which have collinear horizontal bases joined to opposite vertical sides of a vertically elongated rectangular spine edge cover flap. Thus shaped, the preform has the appearance of an isosceles triangle, the center vertex of which is truncated by a horizontal upper edge of the spine cover flap, parallel to the base. The preform preferably includes a horizontally elongated, rectangularly-shaped, first pendent edge cover flap which depends horizontally outwardly from the left hand triangular-shaped portion of the preform, which serves as a first, lower cover flap. A trapezoidally-shaped securement flap depends outwardly from an outer edge of the pendent edge cover flap. Preferably, the securement flap has left and right sides which angle obliquely inwards to an outer or lower edge which is shorter than the upper edge of the securement flap. Also, in the preferred embodiment, the horizontal width of the vertically elongated, spine edge cover flap and the vertical height of the horizontally elongated, pendent edge cover flap have a common value which is slightly larger than the thickness of a picture frame which is to be protected, e.g., about {fraction (15/16)} inch for a frame thickness of about ⅝ inch. Preferably, an upper face of the preform is scored along the vertical sides of the spine edge cover flap and the horizontally disposed upper and lower edges of the pendent edge cover flap to facilitate folding those flaps around intersecting sides of a frame, in a manner described below.

[0022] According to the method of the present invention, a preform, score lines up, is positioned below the corner of an inverted, horizontally disposed picture frame, with the outer side edge walls of a pair of perpendicularly intersecting moldings forming a corner of the frame vertically aligned with the perpendicular sides of the first, left-hand or lower right triangularly-shaped cover flap. A thin, uniform thickness wedge plate which has 45-degree angled side walls that intersect in a front ninety degree vertex angle is also translated horizontally between the preform and the adjacent front face of the inverted frame to vertically align the side walls of the wedge plate vertex with the sides of the underlying lower face cover flap sides and overlying frame molding sides. The pendent edge cover flap and securement flap are then bent vertically upwards to a location adjacent the outer side of a first frame molding, as a planar unit, along the upper or inner score line defining the junction between the base of the lower, left-hand right triangular face cover flap and the pendent edge cover flap. Inward motion of the pendent edge cover flap and securement flap is limited by contact of the inner surface of the securement flap with a first angled side edge of the wedge plate. Thus, even though the cross-section of the frame molding may be nonrectangular, i.e., having a side which is beveled, angled, or arcuately curved between the inverted front surface of the frame adjacent to the preform, and the rear, upper facing surface of the frame, the pendent edge cover flap and securement flap are bent perpendicular to the lower face cover flap, rather than distorted to follow the contour of a non-rectangular cross-section frame molding.

[0023] The securement flap is then bent downwardly and inwardly along the lower or outer score line to contact the upwardly facing, rear face of the first frame molding and towards a horizontal position overlying the first frame molding. Thus bent, the securement flap, pendent edge cover flap and adjacent portion of the lower triangular face cover flap form a U-shaped or C-shaped channel which encloses a front face portion of the frame corner and a portion of the first frame molding adjacent to the corner.

[0024] The right-hand, upper triangular face cover flap and spine edge cover flap are then bent vertically upwards to a position adjacent to the outer side of the second frame molding, as a planar unit along an innermost vertical fold line, i.e., the left-hand vertical edge of the spine edge cover flap. Inward motion of the spine edge cover flap and upper triangular face cover flap is limited by contact of the inner surface of the spine edge cover flap with a second angled side edge of the wedge plate.

[0025] The right-hand, upper triangular face cover flap is then bent downwardly and inwardly along the outermost, right-hand vertical fold line of the spine edge cover flap to a horizontal position overlying the securement flap. Thus bent, the spine edge cover flap and adjacent portions of the lower triangular face cover flap and upper face cover flap form a U-shaped or C-shaped channel which encloses an upwardly facing portion of the frame corner face and a portion of the second frame molding adjacent to the corner. The securement flap is then fastened to both the underlying, first frame molding and the upper triangular face cover flap.

[0026] In one embodiment of the method, suitable for use with wooden frames, a staple is driven through both the overlying upper triangular face cover flap and the securement flap into the underlying first wooden frame molding, thereby securing the flaps together to form a triangular box-like protective cover for the corner, and securing the cover to the frame.

[0027] In another embodiment of the method, a first blob of adhesive is applied between the first frame molding and securement flap, and a second blob of adhesive is applied between the upper surface of the securement flap and the lower surface of the upper triangular face cover flap, whereupon downward pressure is momentarily applied to an upper surface of the upper triangular face cover flap overlying the adhesive blobs, thus adhering the securement flap to both the upper triangular face cover flap and first frame molding. This method of fastening a corner protector is suitable for use with frames made of a wide variety of materials including metal, plastic and wood.

[0028] With a preform attached to a corner of a picture frame as described above, a first, left-hand, lower triangular face cover flap covers a right triangular vertex portion of the front face side of the frame corner, and the pendent rectangularly-shaped edge cover flap covers a portion of the outer side wall of a first molding of a pair of intersecting frame moldings, e.g., the “left-hand” molding. Also, the second, right-hand, upper triangular face cover flap covers a right-triangular portion of the rear face side of the frame, while the rectangularly-shaped spine edge cover flap covers a portion of the outer side wall of a second molding of the frame, e.g., the “right-hand” molding.

[0029] The apparatus according to the present invention includes a base plate or worktable which has a flat upper surface for supporting a picture frame, and a frame holder clamping jig for receiving and holding in a fixed position a corner of the frame on the surface of the table. The apparatus also includes a pair of flap folder mechanisms located on opposite sides of the clamping jig. Each flap folder mechanism includes a flat, rectangularly-shaped flap-contacting arm mounted near a longitudinal end thereof on the upper end of a pedestal which is extendable by a linear actuator from a lower inactive position in which the arm resides within a rectangularly-shaped recess in the upper surface of the base plate, with the upper surface of the arm flush with the upper surface of the base plate, to an upper, active position. Each flap folder mechanism also includes a rotary actuator which is effective in rotating an elevated flap contacting arm ninety degrees from an outer orientation parallel to an outer side of a frame molding and contacting the outer vertically disposed side of a preform flap to an inner, perpendicular orientation, thereby exerting an inwardly and downwardly directed bending force on a flap.

[0030] The apparatus according to the present invention includes a wedge template mechanism which serves as a preform folding guide. The wedge template mechanism includes a thin, uniform thickness wedge plate that has in plan view a polygonal shape which includes a front ninety degree corner vertex formed by the intersection of two straight sides, which are angled at 45 degrees with respect to the longitudinal axis or the wedge plate. The wedge plate mechanism includes a generally rectangularly-shaped support or pusher plate base which is translatably supported above the worktable and attached to a linear actuator which has a longitudinally disposed line of action which bisects the vertex angle of the wedge plate. The wedge plate actuator is effective in retracting the wedge plate to an inactive location rearwards of the frame holder clamping jig, and extending the wedge plate forward to an active position. In the forward, active position of the wedge plate, the two sides of the wedge plate, which intersect to form its front vertex, angle rearwardly and outwardly at 45 degree angles from the vertex. In this forward position, the oblique edges of the wedge plate are located parallel to and proximate the inner perpendicular side edges of the first and second flap folder arms. Moreover, the laterally disposed front edge wall of the wedge plate support pusher plate limits forward motion of a preform to a predetermined location relative to the flap folder arms.

[0031] The corner protector attachment apparatus according to the present invention functions as follows. First, the wedge plate is extended forward to position the vertex and sides of the wedge plate in vertical alignment with inner, mutually perpendicular sides of the flap folder arms. A preform is then slid forward on the worktable surface into position above the first and second flap folder arms. Forward motion of the preform is limited to a predetermined position by contact of the laterally disposed hypotenuse of the lower cover flap of the preform with the front edge wall of the wedge plate support pusher plate. A picture frame is then oriented front face down and the corner of the frame is translated parallel to the upper surface of the worktable to a location underneath the clamping jig, in which the vertex and sides of the frame corner vertically overlie the perpendicular intersecting sides of the lower triangular cover flap portion of the preform. The frame clamping jig is then actuated to clamp the frame in the above-described position. Next, the first corner folder actuator arm is elevated, bending the pendent edge cover flap and securement flap upwardly as a planar unit into a vertical position adjacent to a first frame molding. The first actuator arm is then rotated ninety degrees inwardly towards the frame, thus bending the securement flap inwardly and downwardly into contact with the upper facing, rear surface of the first frame molding.

[0032] The actuator arm of the second corner folder actuator is then elevated, bending the spine edge cover flap and upper triangular face cover protector flap as a planar unit upwards to a position vertically adjacent to the outer edge of the second frame molding. The arm of the first corner folder actuator is then rotated ninety degrees outwardly from its position overlying and holding down the securement flap, while the arm of the second flap folder is simultaneously rotated ninety degrees inwardly, thus bending the upper triangular face cover flap downwardly into contact with the securement flap. The securement flap is then fastened to both the first frame molding and upper triangular cover flap, as by an automatic stapler or adhesive blob dispensing apparatus. Both flap folder arms are then automatically rotated and retracted to their recessed rest positions, flush with the worktable surface. At the same time, the wedge plate is retracted forward, and the frame holding clamp is also automatically released, enabling the frame with attached corner protector to be withdrawn horizontally from beneath the clamping jig. The frame can then be rotated ninety degrees in a horizontal plane, and re-inserted into the clamping jig to initiate another corner protector installation cycle. In this way, a separate corner protector may be attached to each of the three remaining corners of the frame, using the apparatus according to the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033]FIG. 1 is a side perspective view of an automatic corner protector attachment apparatus for frames having non-square cross-section members according to the present invention.

[0034]FIG. 2 is a front elevation view of the apparatus of FIG. 1.

[0035]FIG. 3 is a left side perspective view of the apparatus of FIG. 1.

[0036]FIG. 4 is an upper plan view of the apparatus of FIG. 1.

[0037]FIG. 5 is an upper plan view of the apparatus of FIG. 1, similar to that of FIG. 4, but showing a wedge plate of the apparatus extended to an operative position.

[0038]FIG. 6 is a fragmentary, broken away or skeletal right side elevation view of the apparatus of FIG. 1, showing an actuator mechanism for the wedge plate of FIG. 5 in an extended, operative position.

[0039]FIG. 7 is a view similar to that of FIG. 6, but showing the wedge plate actuator in a retracted position.

[0040]FIG. 8 is a fragmentary left side perspective view of the apparatus of FIG. 1, showing a wedge plate thereof in an extended, operative position.

[0041]FIG. 9 is an upper plan view of a corner protector preform useable with the apparatus of FIG. 1.

[0042]FIG. 10A is a side elevation view of a picture frame in which the side moldings thereof have a rectangular cross section.

[0043]FIG. 10B is a side elevation view of a frame which has chamfered moldings.

[0044]FIG. 10C is a side elevation view of a frame which has radiused moldings.

[0045]FIG. 11AP is a transverse sectional view showing a corner protector preform bent around a rectangular cross section frame molding by a prior art method.

[0046]FIG. 11AI is a view similar to that of FIG. 11AP, but showing a corner protector preform bent around a rectangular cross section frame molding using a template plate according to the method of the present invention.

[0047]FIG. 11BP is a transverse sectional view showing a corner protector preform bent around a chamfered cross section frame molding by a prior art method.

[0048]FIG. 11BI is a view similar to that of FIG. 11BP, but showing a corner protector preform bent around a chamfered cross section frame molding using a template plate according to the method of the present invention.

[0049]FIG. 11CP is a transverse sectional view showing a preform bent around a radiused cross section frame molding by a prior art method.

[0050]FIG. 11CI is a view similar to that of FIG. 11CP, but showing a preform bent around a radiused cross section frame molding using a template plate according to the method of the present invention.

[0051]FIG. 12A is an upper plan view of a wedge plate of the apparatus of FIG. 1.

[0052]FIG. 12B is a lower plan view of the wedge plate of FIG. 12A.

[0053]FIG. 12C is a side elevation view of the wedge plate of FIGS. 12A and 12B.

[0054]FIG. 12D is a fragmentary upper plan view of the apparatus of FIG. 1, showing a preform of the type shown in FIG. 9 advanced towards a frame clamping jig of the apparatus and into an installation position, and a wedge plate of the apparatus extended over the preform.

[0055]FIG. 12E is a fragmentary upper plan view of the apparatus of FIG. 1, showing a preform of the type shown in FIG. 9 advanced towards a frame clamping jig of the apparatus and into an installation position, a wedge plate of the apparatus extended over the preform, and a corner of an inverted picture frame inserted into the frame clamp above the wedge plate.

[0056]FIG. 13A is a rear perspective view of the apparatus of FIG. 1.

[0057]FIG. 13B is a view similar to that of FIG. 13A, but showing a stack of corner protector preforms or blanks in a feed position on the apparatus.

[0058]FIG. 13C is a view similar to that of FIG. 13B, but showing the stack of preforms removed, and showing a single preform advanced into an installation position adjacent to a frame clamping jig of the apparatus, and showing a wedge plate of the apparatus extended forward into and operative position over the preform.

[0059]FIG. 13D is a view similar to that of FIG. 13C, but showing a corner of a picture frame inserted into an operative installation position within an opening in clamping jig of the apparatus, above the wedge plate and preform, and showing a clamp bar of the clamping jig actuated downwards into clamping contact with the upper facing, rear surface of the intersecting frame moldings.

[0060]FIG. 13E is an upper plan view of the arrangement of FIG. 13D.

[0061]FIG. 14 is a view similar to that of FIG. 13D, but showing a first corner flap actuator comprising part of the apparatus in an upwardly actuated position.

[0062]FIG. 15 is a view similar to that of FIG. 14, but showing a fold-effecting, flap folder arm of the first corner flap actuator rotated to contact and fold down a securement flap of the corner protector preform into a position overlying the picture frame.

[0063]FIG. 16 is a view of the apparatus of FIG. 1 similar to that of FIG. 15, but showing a second corner flap actuator of the apparatus in an upwardly actuated position.

[0064]FIG. 17 is a view similar to that of FIG. 15, but showing a flap folder arm of the second corner flap actuator rotated to contact and fold down a second, upper triangular corner flap of the corner protector preform into a position overlying the securement flap of the corner protector preform.

[0065]FIG. 18 is a view of the apparatus of FIG. 1 similar to that of FIG. 17, but showing the flap folder arm of the first corner flap actuator rotated back into an inactive, home position and showing a stapler comprising part of the apparatus inserting a staple through an upper triangular corner flap and securement flap into the picture frame.

[0066]FIG. 19 is an upper plan view of the apparatus of FIG. 1, showing the flap folder arm of the second corner flap actuator rotated back to a home position and showing the stapler of FIG. 18 elevated to a home position.

[0067]FIG. 20 is a perspective view showing a completed corner protector installation, and showing a preform pusher plate of the apparatus partially retracted to a home position.

[0068]FIG. 21 is a view similar to that of FIG. 20, but showing the pusher plate fully retracted.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] FIGS. 1-21 illustrate various aspects of an automatic corner protector attachment method and apparatus for frames having non-rectangular cross-section moldings according to the present invention. Certain components of the apparatus according to the present invention are substantially similar in structure and function to those described in detail in the present inventor's U.S. Pat. No. 6,018,934. Accordingly a more detailed understanding of those components may be obtained by referring to U.S. Pat. No. 6,018,934, the entire disclosure of which is hereby incorporated by reference thereto into the present disclosure. Also, the entire disclosure of the present inventor's U.S. Pat. No. 6,418,708, and application Ser. No. 09/927,949, filed Aug. 10, 2001, are hereby incorporated by reference thereto in the present disclosure.

[0070]FIGS. 10A, 10B, and 10C illustrate picture frame moldings having rectangular, chamfered and radiused front edge surfaces, respectively, of types useable with the method and apparatus of the present invention.

[0071] FIGS. 11AP, 11BP, and 11CP show corner protector forms in the process of being bent around frame corners formed by the intersection of frame moldings having the shapes seen in FIGS. 10A, 10B, 10C, respectively, and showing the misshapen bent preforms for the non-rectangular cross section moldings on FIGS. 11BP and 11CP.

[0072] FIGS. 11Ai, 11BI, and 11CI illustrate properly shaped, bent preforms achieved using the method and apparatus of the present invention.

[0073] Referring now to FIG. 14, an apparatus 20 for attaching corner protectors to the corners of picture frames which may have non-rectangular cross-section frame molding members may be seen to include a generally rectangular box-shaped enclosure 21 surmounted by a generally flat upper base plate or worktable 22. As shown in the figures, apparatus 20 includes an elongated, generally straight frame folding/clamping jig 23 mounted on the upper surface 24 of worktable 22, near front wall 65 of enclosure 21. Clamping jig 23 includes an elongated straight beam member or support plate 25 which is disposed laterally with respect to worktable 22, and supported above upper surface 24 of worktable 22 by a pair of laterally opposed, left and right clamp support/frame molding guide bars 26L, 26R, respectively. Support guide bars 26L, 26R have flat and parallel lower and upper surfaces 226, 227, respectively, the upper surfaces supporting clamp beam member 25 so that its lower surface 27 is parallel to and spaced above upper surface 24 of the worktable.

[0074] As shown in FIG. 4, left and right support bars 26L, 26R have inner longitudinally disposed vertical wall surfaces 228L, 228R, respectively, which are perpendicular to upper surface 24 of worktable 22. As is also shown in FIG. 4, the longitudinal axes of support bars 26L, 26R are each oriented at 45 degrees to a longitudinal center line of worktable 24, so that if inner vertical surfaces 228L, 228R of support bars 26L, 26R were extended rearwardly towards the center of worktable 24, those surfaces would intersect to form a right dihedral angle corner. However, as shown in FIG. 4, support bars 26L, 26R have obliquely inclined rear face walls 229L, 229R, respectively, that are angled at 45 degrees to inner vertical side walls 228L, 228R of the support bars, the rear faces lying in a common vertical plane disposed laterally, i.e., perpendicularly with respect to the longitudinal center line of worktable 24. Thus arranged, inner vertical side walls 228L, 228R of support bars 26L, 26R are mutually perpendicular, and form guide surfaces along which may slide the outer side walls of a pair of mutually perpendicular picture frame moldings which intersect to form a ninety degree frame corner. As shown in FIGS. 4 and 12, a laterally disposed space 230 between opposed inner corners 231L, 231R of support bars 26L, 26R enables the corner of a frame to be slid diagonally rearwards beneath clamping jig 23 along guide surfaces 228L, 228R to thereby protrude forward beyond front face walls 229L, 229R of the support bars.

[0075] As shown in FIGS. 1 and 13, clamping jig 23 includes a plate-like clamp bar 28 which has parallel upper and lower surfaces 28T, 28B, parallel straight front and rear edges 28A, 28P, and obliquely angled side edges 28L, 28R. Clamp bar 28 is located below and vertically aligned with clamp beam member 25, and vertically actuable up and down with respect to the clamp beam member by supplying pressurized air to a double-action pneumatic clamp actuator cylinder 30.

[0076] Apparatus 20 according to the present invention also includes a feeder mechanism 60 for feeding in a forward direction an individual corner protector preform 40, of the type shown in FIG. 9 and described below, to a predetermined position beneath clamping jig 28, prior to inserting the corner of a frame to be protected rearwards into opening 230 in the clamping jig.

[0077] As shown in FIG. 9, preform 40 is made of a thin sheet of readily bendable material, such as corrugated cardboard. Preform 40 has two laterally mirror symmetric, right triangularly-shaped face cover flaps 41, 42, respectively. One of the triangularly-shaped face cover flaps, e.g., left-hand face cover flap 41 in FIG. 9, has a laterally elongated, rectangularly-shaped, first, “pendent” edge cover flap portion which depends downwardly from base 43 of left-hand, lower face cover flap 42. A trapezoidally-shaped securement flap 51 depends downwardly from the bottom edge wall 52 of pendent edge cover flap 50, the securement flap having an upper edge wall coextensive with bottom edge wall 52 of the pendent edge cover flap, and a lower edge wall 53 parallel to but shorter than edge wall 52.

[0078] Referring still to FIG. 9, it may be seen that left, lower right triangular face cover 41 and right, upper right triangular face cover flap 42 having collinear horizontal bases 43, 44, respectively. Bases 43 and 44 are joined at their respective ninety degree corner angles to opposite, left and right, vertical sides 45, 46 of a vertically elongated, rectangularly-shaped, second, “spine” edge cover flap 47. Spine edge cover flap 47 has a base 48 collinear with the bases of triangular lower and upper cover flaps 41, 42. Thus shaped, the upper symmetric portion of preform 40 has a plan-view shape approximating that of an isosceles triangle that has a base 43-43-44 and an upper, center vertex truncated by a horizontal edge 49 parallel to the base.

[0079] In a preferred embodiment of corner protector preform 40, the width of spine edge cover flap 47 and the height of pendent edge cover flap 50 are both equal to a common value which is slightly greater than the thickness of a picture frame corner which the preform is to be used to protect, e.g., about {fraction (15/16)} inch for a frame molding thickness of ⅞ inch. As shown in FIG. 9, the upper face of preform 40 is preferably scored along vertical edge walls 45 and 46 of spine edge cover flap 47, and along horizontal edge walls 43 and 52 of pendent rectangular edge cover flap 50. The score lines are located along boundaries between adjacent flaps, and facilitate bending the flaps from the plane of the preform and folding the flaps around a frame corner, as will be explained below.

[0080] Referring now to FIGS. 1 and 13A, apparatus 20 may be seen to include a corner protector preform feeder mechanism 60 that has a longitudinally elongated, rectangularly-shaped guide plate 61 which has a generally flat surface located above and parallel to upper surface 24 of worktable 22. Guide plate 61 is oriented with its long axis parallel to left and right side walls 62 and 63 of enclosure 21, and protrudes rearward of rear side wall 64 of the enclosure. Also, guide plate 61 of feeder mechanism 60 has through its thickness dimension a perforation 66 which has substantially the same outline shape as corner protector preform 40. Guide plate 61 is spaced above upper surface 24 of worktable 22 at a distance slightly greater than the thickness of corner protector preform, e.g., {fraction (5/16)} inch for preforms having a thickness of about ¼ inch. Thus, a corner protector preform placed congruently over perforation 66 will drop through the perforation onto worktable surface 22, enabling the preform to be slid forward into operating position relative to clamping jig 23, as will be described in detail below.

[0081] As shown in FIG. 1, a stack of preforms 40 is maintained in vertical alignment above guide plate perforation 66 by a plurality of vertically disposed guide rods 67 which protrude upwardly from guide plate 61, around the perimeter of perforation 66. A vertically downwardly directed force is exerted on the stack of preforms 40 by the weight of a flat, uniform thickness weight block 68 which has through it thickness dimension a plurality of clearance bores 68B which insertably receive the upper ends of guide rods 67, thus enabling the weight block to remain in contact with the upper preform in a stack and slide downwardly on the rods as the stack height is lowered as a result of preforms being fed out from the bottom of the stack.

[0082] As shown in FIGS. 1, 13A, 19 and 20, preform feeder mechanism 60 includes a pusher plate 69 longitudinally slidably located below guide plate 61. Pusher plate 69 has a generally uniform thickness, and has a front edge wall 73 in which is formed a notch which has a shape complementary to that of the lower, or rear, edge wall of a preform 40. Preferably, pusher plate 69 is made of a structural polymer such as DELRIN, NYLON, or similar material which has good lubricity. Pusher plate 69 is automatically actuable by a double action pneumatic cylinder (not shown) located with the enclosure 21, in both forward and backward directions, through reciprocating motion of piston rod 84.

[0083] Corner protector attachment apparatus 20 also includes an automatic stapler mechanism 91 which includes a stapler gun 92 and an automatic actuator for lowering the stapler gun into position above a corner protector preform 40 that has been bent around a frame corner, inserting a staple, and retracting the stapler upwards to a home position.

[0084] Referring now to FIGS. 4 and 16, corner protector installation apparatus 20 may be seen to include a pair of corner protector preform flap folder mechanisms 120L and 120R located on the left and right sides, respectively, of the apparatus, as viewed from the rear of the apparatus. As shown in FIG. 1, flap folder mechanisms 120L, 120R are located longitudinally rearwards or inwards of clamping jig 23, at a location that places the mechanisms adjacent to the intersecting side moldings of a frame inserted rearward into space 230 beneath clamp bar 28 of the clamping jig. Flap folder mechanisms 120L, 120R are identical in structure and function. Therefore, in the ensuing description, the flap folder mechanisms may generally be referred to without a letter description.

[0085] As shown in FIGS. 1, 4, and 16, each flap folder mechanism 120 such as left-hand flap folder mechanism 120L includes a flat, rectangularly-shaped flap folder arm 121 which fits into a complementary-shaped recess 119 formed in upper surface 24 of worktable 22, flush with the upper surface. Flap folder arm 121 is oriented with a long, inner longitudinal edge 122 thereof parallel and adjacent to a side of one molding of picture frame corner which has been inserted horizontally into space 230 beneath clamp bar 28 to thus position the frame so that a corner of the frame protrudes rearwardly from beneath clamp bar 28 of clamping jig 23, to a position in which two sides of frame molding intersecting at the frame corner are adjacent to inner longitudinal edges 122L, 122R of flap folder arms 121L, 121R.

[0086] As shown in FIG. 16, flap folder arm 121 of each flap folder mechanism 120 is mounted on the upper end 123 of a vertically disposed, cylindrically-shaped support post 124. Support post 124 is in turn rotatably mounted at its lower end in a manner enabling the support post to rotate about a vertically disposed, longitudinal axis of the post. Each flap folder mechanism 120 includes a rotary actuator (not shown) which is effective in individually rotating a selected flap folder arm 122 from an orientation parallel to a frame molding, as shown in FIGS. 1 and 4, inwardly towards the interior of the frame, as shown in FIGS. 16 and 17. In a preferred embodiment, each flap folder arm 122 is rotatable parallel to upper surface 24 of worktable 22 ninety degrees inwardly from an orientation parallel to recess 119, and back to that orientation.

[0087] As may be understood by comparing FIGS. 1 and 4 with FIG. 16, each corner flap folder mechanism 120 includes a linear actuator (not shown) which is effective in individually elevating and lowering a selected flap folder post 124, thus elevating a flap folder arm 121 from a home position in a recess 119 of worktable 22, as shown in FIGS. 1 and 4, to an elevated position, as shown in FIG. 16, and lowering the flap folder arm into the recess.

[0088] Referring now to FIGS. 1, 4-8, and 12A-12E, apparatus 20 may be seen to include a wedge template mechanism 300 which includes a wedge plate 301 for positioning between the corner of a frame and a preform prior to bending flaps from the preform around the corner. Thus positioned, wedge plate 301 serves as a bending template which ensures that flaps are bent perpendicularly upwards from the plane of the preform into positions parallel to the sides of intersecting frame corner moldings, even if the sides do not intersect the front face at a ninety degree angle, i.e, if the sides are obliquely angled or curved.

[0089] As shown in FIG. 12A, wedge plate 301 of wedge template mechanism 300 has in upper plan view a rectangularly-shaped lower, or front portion 302 and an upper, or rear triangularly-shaped portion 303. The specific shape of front portion 303 of wedge plate 301 is that of an isosceles right triangle, the hypotenuse 304 of which is laterally disposed and coextensive with the upper lateral edge of lower rectangularly-shaped portion 302 of the wedge plate. Thus, upper triangularly-shaped portion 303 of wedge plate 301 has a laterally centrally located, upwardly pointing 90 degree vertex 305. Vertex 305 is formed by the intersection of straight side edges 306, 307, which angle at 45 degrees with respect to the longitudinal center line of wedge plate 301, and downwardly and outwardly from the vertex to hypotenuse 304. Preferably, vertex 305 has a convex, arcuately curved, or radiused, outer surface 308.

[0090] As shown in FIGS. 12B and 12C, wedge plate 301 of wedge template mechanism 300 has a generally uniform thickness of about ⅛th inch and is supported by a generally rectangularly-shaped support or pusher plate base 309, which has a uniform thickness of about 0.145 inch. Wedge plate 301 is preferably made of a structural polymer such as DELRIN or NYLON. Pusher plate base 309 is preferably made of a metal such as aluminum, and has a straight, transversely disposed forward vertical edge wall 309A.

[0091] As may be seen best by referring to FIGS. 4-7, wedge template mechanism 300 includes a linear actuator 310 for translating wedge plate 301 parallel to upper surface 24 of worktable 22 from a forward, home position, as shown in FIG. 4, to a rearward active position as shown in FIGS. 5, 6, and 8. As shown in FIGS. 5, 6, and 7, linear actuator 310 of wedge template mechanism 300 includes a longitudinally elongated, generally rectangularly-shaped track base plate 311 which is disposed longitudinally rearward in a similarly-shaped recess 312 which protrudes rearwards from front wall 65 of worktable 24, midway between left and right side walls of the worktable. Track base plate 311 has through its thickness dimension a laterally centrally located, longitudinally disposed slot 313. A pair of screws 314 protrudes downwardly through a pair of longitudinally aligned, laterally centered holes 315 through wedge plate 310, the lower ends of the screws being secured in a follower block 316 of a magnetically coupled pneumatic actuator cylinder 317. Pneumatic actuator cylinder 317 has protruding forward from a front end thereof a horizontally disposed tube 318 which is slidably received through a bore 319 through follower block 316. Tube 318 of pneumatic actuator cylinder 317 encloses piston rod magnet (not shown) attached to a piston rod (not shown) which is selectably extendable forwards and retractable rearwards in response to pressurized air supplied to the pneumatic actuator. Follower block 316 contains a follower magnet (not shown) which is magnetically coupled to the piston rod magnet, thus advancing the follower block and attached wedge template 301 forward to a home position when the piston rod is extended, as shown in FIG. 7, and retracted rearward to an active position when the piston rod is retracted, as shown in FIG. 6.

Operation of the Invention

[0092] Apparatus 20 according to the invention includes components such as a programmable logic controller for issuing a predetermined, automatic sequence of electrical command signals to operate various control elements of the apparatus such as solenoid valves which are used to control the flow of pressurized air to various pneumatic force actuator cylinders of the apparatus. The sequence is effective in automatically installing a corner protector onto a frame corner, when the corner is correctly positioned with respect to the clamping jig and flap folder arms. The structures and functions of the foregoing components are well know to those skilled in the art, and are described in detail in the present inventor's U.S. Pat. No. 6,018,934. Also, mechanisms for further automating the apparatus disclosed herein are disclosed in the present inventor's U.S. Pat. No. 6,418,700. Therefore, to enhance the clarity of the present disclosure, certain of the foregoing components are not shown herein.

[0093] Following is a typical sequence of operation of apparatus 20 according to the present invention.

[0094] 1. A vertical stack of corner protector preforms 40 is loaded onto feeder mechanism 60 (FIG. 13B).

[0095] 2. Electrical power and pressurized air are supplied to the apparatus, and a programmable logic controller (PLC) resets and checks the system, readying the PLC for outputting sequence commands to a solenoid valve bank. The program for the sequence is stored in a computer memory in the PLC. The program can be changed, modified or run via a computer.

[0096] 3. Pneumatic actuator cylinder 317 of wedge plate template mechanism 300 is energized, thus moving wedge plate 301 rearward into position beneath clamping jig 23, as shown in FIGS. 12D and 13C. At the same or a slightly delayed time, the actuator cylinder of feeder mechanism 60 is energized to draw piston rod 84 of the feeder mechanism forward, thereby moving a single corrugated corner protector preform blank 60 forward into position below clamp bar 28. Forward motion of the preform 40 to a precisely predetermined location relative to the inner facing longitudinal edges of flap folders 121L, 121R is limited by contact of leading, hypotenuse edge of lower triangular cover flap portion 41 of the preform with front transversely disposed edge wall 309A of wedge plate pusher plate base 309.

[0097] 4. Referring to FIG. 13D, a picture frame A which has a first, e.g., left-hand frame molding B which intersects a second, e.g., right-hand frame molding D at a 90-degree corner C is oriented with the front, ornate face E of the frame facing downward to and parallel with upper surface 24 of worktable 22. The frame is rotationally oriented so that the corner C points diagonally to front opening 230 beneath clamping jig 23, e.g., with the diagonal of corner C aligned with a longitudinal, fore-and-aft center line of clamping jig 28. Corner C of the frame is then inserted beneath clamping jig 23, with left and outside side edges E and F of moldings B and D vertically aligned with edges 43 and 45 of preform 40, and with edges 306 and 307 of wedge plate 301. When frame corner C is properly aligned with wedge plate 301 and preform 40, clamp actuator cylinder 38 is energized, thus forcing clamp bar 28 downwards into contact with portions of the upper facing rear surface of moldings B and D of frame A.

[0098] 5. A first bend of first, pendent rectangular cover flap 50 and securement flap 51 of preform 40 together as a planar unit is accomplished by elevating left-hand flap folder arm 121L, with the flap folder arm in its clockwise, home orientation, as shown in FIG. 14.

[0099] 6. A second bend of securement flap 51 inwardly and downwardly over left-hand frame molding B is effected by rotating left flap folder arm 121L ninety degrees counterclockwise towards the inside of the frame, as shown in FIG. 15.

[0100] 7. A third bend of upper, right-hand triangular face cover flap 42 and spine edge cover flap 47 together as a planar unit is effected by elevating right-hand flap folder arm 121R, with the flap folder arm in its counterclockwise, home orientation, as shown in FIG. 16.

[0101] 8. A fourth and final bend of upper triangular face cover flap 42 inwardly and downwardly over the upper facing rear surface of right-hand frame molding D is effected by rotating right-hand flap folder arm 121R ninety degrees clockwise towards the inside of the frame, as shown in FIG. 17. At the same time, left-hand flap folder arm 121L is rotated clockwise to its home orientation.

[0102] 9. Staple gun 92 is lowered until the lower head face of the staple gun contacts the upper surface of upper face cover flap 42 overlying securement flap 52 and left-hand frame molding B, whereupon an automatic firing trigger causes a staple to be discharged from the gun upon contact with upper cover flap, thus firing a staple through the upper triangular cover flap and securement flap into the left-hand front molding B. This action completes the folding of preform 40 into a finished corner protector, and the attachment of the corner protector to corner C of frame A.

[0103] 10. Right-had flap folder arm 121R is rotated ninety degrees counterclockwise to the home orientation.

[0104] 11. Left-hand flap folder arm 121L and right-hand flap folder arm 121R are lowered to their home position in worktable surface recesses 119L, 119R, respectively.

[0105] 12. Clamp actuator cylinder 30 is energized to raise clamp bar 28, thus unclamping frame A.

[0106] 13. Wedge plate 301 is retracted forward to its home position. Frame A is removed from clamping jig 23 by withdrawing the frame forward from apparatus 20.

[0107] 14. Wedge plate 301 is extended rearward to its active position.

[0108] 15. Feeder mechanism 60 is actuated to feed another corner protector preform blank 40 into position adjacent to clamping jig 23.

[0109] 16. A new frame corner to be protected is inserted under clamp bar 28, and steps 4-13 repeated for each such corner, typically all four corners of a frame. 

What is claimed is:
 1. A method for attaching a protective cover to a corner of a frame having front and rear face surfaces, said corner being formed by an intersection at a dihedral frame angle of two adjacent frame moldings comprising two adjacent sides of said frame, each of said frame moldings having an outer side which intersects said front and rear surfaces of said frame at arbitrary front and rear molding angles in a transverse cross sectional view, said method comprising; a. placing said frame corner front face down over a flat corner protector preform comprising a thin sheet of flexible material, said sheet being bendable into a plurality of flaps to enclose portions of said front and rear frame surfaces and said sides of said moldings adjacent to said frame corner, b. positioning a thin template plate having a vertex angle congruent with said dihedral frame corner angle between said preform and said frame corner with intersecting sides of said template forming said vertex thereat in congruent alignment with said rear side edges of said frame moldings intersecting to form said frame corner, c. bending from a horizontal plane of said preform first and second, vertically disposed flap sections which contact said first and second edges, respectively, of said template, d. bending an upper part of each of said first and second flap sections perpendicularly inwards to a horizontal disposition overlying said rear surface of said frame, and e. securing said overlying parts of said flap sections to each other and to said rear surface of said frame.
 2. The method of claim 1 wherein at least a part of said outer side of said frame molding is further defined as being obliquely angled with respect to said front and rear surfaces of said frame.
 3. The method of claim 1 wherein at least a part of said outer side of said frame molding is further defined as being contoured.
 4. The method of claim 1 wherein said plan view dihedral frame corner angle is further defined as being substantially a right angle.
 5. The method of claim 4 wherein said preform is further defined as having a first, right triangularly-shaped lower, front face cover flap, the sides of which are vertically aligned with said edges of said template and said rear side edges of said intersecting moldings.
 6. The method of claim 5 wherein said preform is further defined as including a first, rectangularly-shaped, pendent side cover flap which protrudes outwardly from a horizontal base side of said lower right triangularly-shaped, front face cover flap.
 7. The method of claim 6 wherein said first, pendent side cover flap is bent perpendicularly up from the plane of said preform to lodge vertically against a first edge of said template plate and a rear edge of a first molding of said frame.
 8. The method of claim 7 wherein said preform is further defined as having a securement flap which protrudes outwardly from an outer horizontal edge of said pendent side cover flap parallel to said base of said triangularly-shaped lower face cover flap, said securement flap having an outer perimeter edge parallel to said base and said outer horizontal edge of said pendent side cover flap.
 9. The method of claim 8 wherein said securement flap is bent perpendicularly downwards and inwards towards said first frame molding along a securement flap fold line coincident with said outer horizontal edge of said pendent side cover flap, to overlie a portion of said rear face of said first molding.
 10. The method of claim 9 wherein said securing step includes fastening said securement flap to an upper facing rear surface of said first molding.
 11. The method of claim 10 wherein said securement flap is further defined as having an outer perimeter edge parallel to but shorter than said securement flap fold line, thereby giving said securement flap a horizontally elongated, trapezoidal shape.
 12. The method of claim 9 wherein said preform is further defined as including a second, rectangularly-shaped, vertically elongated spine side cover flap which depends outwardly from a vertical altitude side of said lower triangularly-shaped front face cover flap.
 13. The method of claim 12 wherein said second, spine edge cover flap is bent perpendicularly upwards from the plane of said preform along said altitude edge of said preform to lodge vertically against a second edge of said template plate and a rear edge of a second molding of said frame.
 14. The method of claim 13 wherein said preform is further defined as having a second, upper right-triangularly-shaped, rear face cover flap which protrudes outwards from an outer vertical joint edge of said spine edge cover flap parallel to said altitude side of said triangularly-shaped lower face cover flap.
 15. The method of claim 14 wherein said upper triangularly-shaped rear face cover flap is bent perpendicularly downwards along said outer vertical joint line with said spine edge cover flap to overlie a portion of said rear face of said frame including portions of said first and second moldings.
 16. The method of claim 15 wherein said securing step includes fastening said upper triangular cover flap to an upper surface of said securement flap.
 17. An apparatus for attaching a protective cover to a corner of frame having front and rear face surfaces, said corner being formed by an intersection at a dihedral frame corner angle of two adjacent, first and second frame moldings comprising two adjacent, first and second sides of said frame, each of said frame moldings having an outer side which intersects said front and rear surfaces of said frame at arbitrary front and rear molding angles, respectively, said protective cover being made from a preform composed of a thin sheet of flexible material, said apparatus comprising; a. means for positioning a template plate having first and second side edges which intersect at a dihedral vertex angle and which are congruently alignable with sides of said first and second moldings and said frame, respectively, between said corner protective preform and said frame corner with said first and second side edges of said template vertically aligned with side edges of said first and second frame moldings, respectively, b. means for bending upwardly from a horizontal plane of said preform first and second, vertically disposed flap sections which contact said first and second edges, respectively, of said template, c. means for bending inwardly an upper part of each of said first and second flap sections perpendicularly to horizontal dispositions overlying said rear surface of said frame, and d. means for securing said overlying parts of said first and second flap sections to each other and to said rear surface of said frame.
 18. The apparatus of claim 17 wherein said means for bending upwardly from said horizontal plane of said preform said first flap section is further defined as comprising in combination a first flap folder arm attached to an upper end portion of a first support post, first elevator actuator means for selectably elevating and retracting said first flap folder arm, and a first, front flap folder arm recess in an upper surface of a worktable, said first recess being located below said preform and adjacent to a side of said first frame molding and below said first flap section of said preform, whereby elevation of said first flap folder arm by said first elevator actuator means forces said first flap section to bend upwardly with respect to said surface of said preform to lodge vertically against said first edge of said template plate.
 19. The apparatus of claim 18 wherein said means for bending perpendicularly inwardly from said first flap section an upper part which overlies said rear surface of said frame is further defined as comprising a first rotary actuator means coupled to said first flap folder arm, said first rotary actuator means being effective in rotating said first flap folder arm from a home elevated position vertically aligned with said first flap folder arm recess inwardly towards said first frame molding to an active elevated position overlying said first frame molding, thereby bending said upper part of said first flap section over said first frame molding.
 20. The apparatus of claim 19 wherein said means for bending upwardly from said horizontal plane of said preform said second flap section is further defined as comprising in combination a second flap folder arm attached to an upper end portion of a second support post, second elevator actuator means for selectably elevating and retracting said second flap folder arm, and a second front flap folder arm recess in an upper surface of said worktable, said second recess being located below said preform and adjacent to a side of said second frame molding and below said second flap section of said preform, whereby elevation of said second flap folder arm by said second elevator actuator means forces said second flap section to bend upwardly with respect to said surface of said preform to lodge vertically against said second edge of said template plate.
 21. The apparatus of claim 20 wherein said means for bending perpendicularly inwardly from said second flap section an upper part which overlies said rear surface of said frame is further defined as comprising a second rotary actuator means coupled to said second flap folder arm, said second rotary actuator means being effective in rotating said second flap folder arm from a home elevated position vertically aligned with said second flap folder arm recess inwardly towards said second frame molding to an active elevated position overlying said second frame molding, thereby bending said upper part of said second flap section over said second frame molding.
 22. The apparatus of claim 17 wherein said means for positioning said template plate between said preform and said frame corner is further defied as comprising in combination; a. a worktable having an upper surface for supporting a preform, b. means for positioning an individual preform at a predetermined location on said upper surface of said worktable, c. means for positioning a corner of a frame at a predetermined location relative to said preform, and d. template linear actuator means for advancing said template forward to an operative position between said preform and said frame prior to said preform being bent around said frame corner, and retracted to a home position thereafter.
 23. The apparatus of claim 22 wherein said template plate is further defined as having triangularly-shaped laterally symmetric front portion, and a longitudinal center line parallel to a line of action of said template plate linear actuator.
 24. The apparatus of claim 23 wherein said template plate is further defined as being mounted on the upper surface of a support base, said support base having a transversely disposed front edge wall located rearwards of said front triangular portion of said template plate.
 25. The apparatus of claim 24 wherein said means for positioning an individual preform at a predetermined location on said upper surface of said worktable is further defined as comprising in combination a preform pusher plate, and a preform linear actuator for advancing an individual preform forward into a predetermined operative position on said upper surface of said worktable, and retracting said pusher plate to a rearward home position.
 26. The apparatus of claim 25 wherein forward motion of said preform to said predetermined operative position is limited by contact of said preform with said front edge wall of said template plate base.
 27. In a method for folding a flexible material around a corner of a frame having front and rear face surfaces to thereby form a protective cover for said corner, said corner being formed by an intersection at a dihedral angle of two adjacent, first and second sides of said frame, the improvement comprising; a. positioning a thin template plate which has in plan view a wedge-shaped forward portion approximating that of an isosceles triangle which has a transversely disposed base and equal length sides which angle forward and inwards towards a longitudinal center line comprising an altitude of the triangle and which intersect at a vertex angle to form a forward protruding vertex, between said flexible material and a face of said frame, with said vertex and sides of said template plate symmetrically positioned with respect to said sides and corner of said frame, and b. bending from a plane containing said material towards said first and second sides of said frame first and second flap sections for subsequent bending over a face of said frame, inward motion of said first and second flap sections being limited by contact between first and second flap sections and said first and second sides, respectively, of said template plate.
 28. The method of claim 27 wherein said vertex angle of said template plate is substantially equal to ninety degrees.
 29. The method of claim 28 wherein said dihedral frame angle is substantially equal to ninety degrees.
 30. In an apparatus for attaching a protective cover to a corner of a frame having front and rear face surfaces, said corner being formed by an intersection at a dihedral frame corner angle of two adjacent, first and second sides of a frame, said protective cover being made of a thin sheet of flexible material, the improvement comprising; means for positioning a template plate which has first and second side edges that intersect at a dihedral template vertex angle which is substantially congruently alignable with said first and second sides and dihedral frame corner angle, respectively, between said thin sheet of flexible material and a face surface of said frame, whereby bending motion of first and second flap sections from said thin sheet of material towards said first and second sides of said frame is limited by contact between said first and second flap sections and said first and second sides, respectively, of said template plate.
 31. The apparatus of claim 30 wherein said vertex angle of said template plate is substantially equal to ninety degrees.
 32. The method of claim 31 wherein said dihedral frame angle is substantially equal to ninety degrees. 